The invention relates to a circuit for use in a receiver which is arranged for receiving two-tone/stereophonic programs, each program being accompanied by a pilot signal each having a different characteristic frequency.
Future television broadcasts will be accompanied by either a mono signal, or a stereo signal, or by a two-tone signal. Said last signal is a signal consisting of two mutually independent and different signals, namely a signal A and a signal B. Said signals will particularly be employed for the transmission of spoken text. The signal A then represents, for example, a Dutch version and the signal B, for example, an English version of that text. In order to enable the receiver to know whether a two-tone or a stereophonic program is being broadcast a pilot signal is also transmitted. A signal having a characteristic frequency is modulated on this pilot signal which has a frequency of, for example, 45 kHz. Said characteristic frequency is for example, equal to 117 Hz when a stereo signal is transmitted and 274 Hz when a two-tone signal is transmitted. There are now four possibilities at the receiving end, namely either stereo or mono, or signal A or signal B.